1. Field of the Invention
The present invention relates to a method of forming a lubricative plated layer on a viscous liquid feed nozzle and the viscous liquid feed nozzle itself, the viscous liquid feed nozzle is used when manufacturing, for example, a head suspension that is arranged in a disc drive incorporated in an information processor such as a personal computer.
2. Description of Related Art
The viscous liquid feed nozzle is installed on a viscous liquid feed unit and is used to feed, for example, a viscous adhesive to attach a piezoelectric element to a head suspension employing a dual actuator system.
The piezoelectric element is very small, and therefore, the viscous liquid feed nozzle must feed a very small quantity of viscous adhesive to the piezoelectric element. For this, the nozzle is thin and long and has a large aspect ratio with, for example, about 0.05 to 0.4 mm in inner diameter and several millimeters in length. When repeatedly feeding a small quantity of viscous adhesive, the nozzle is entangled with the adhesive that forms threads or balls to destabilize the feeding of the adhesive in a predetermined quantity.
To solve this problem, Japanese Unexamined Patent Application Publication No. H11-07897 discloses a nozzle made of a water repellent material and a nozzle whose front end is coated with a water repellent material. Also, Japanese Unexamined Patent Application Publication No. H11-330679 discloses a nozzle whose inner circumference is provided with water repellence.
Nozzles having a relatively large inner diameter such as 0.5 mm may be producible from a water repellent material. Nozzles having smaller diameters, however, are difficult to produce from a water repellent material. Even if they are producible from, for example, water repellent resin, they have low rigidity and are improper for precise positioning when applying a viscous liquid to a small object such as the piezoelectric element.
Water repellence of the viscous liquid feed nozzle is generally realized by coating the nozzle with a fluorine film such as a Teflon (registered trademark) film. The fluorine coating is difficult to carry out on the inner circumference of a thin and long nozzle having a large aspect ratio of 0.05 to 0.4 mm in inner diameter and several millimeters in length.
Furthermore, the fluorine coating is usually carried out by powder coating or electrostatic spraying. These coating techniques are hardly applicable to the inner circumference of a very small hole of the nozzle.
This is because the powder coating is unable to uniformly supply powder into the small hole. In the case of the electrostatic spraying, a problem occurs as illustrated in FIG. 5. Namely, the electrostatic spraying causes a concentration of power lines at a front end 103 of a nozzle 101 to partly thicken the coating at the front end 103. On the other hand, no power line enters a very small hole 105 of the nozzle 101, so that no coating is formed in the hole 105. The thickened coating 107 at the front end 103 of the nozzle 101 increases a risk of blocking a feed port of the hole 105.
The thickened coating 107 at the front end 103 will form threads or balls to further destabilize a quantity of viscous liquid to be fed from the nozzle 101.
In addition, the fluorine coating needs a baking process that is carried out at about 400 degrees centigrade, and therefore, is inapplicable to a nozzle that is already heat-treated.
An immersion technique may be employed to form a water repellent coating on the viscous liquid feed nozzle. This technique applies liquid paint to the nozzle and dries the paint on the nozzle, and therefore, the technique has a risk of closing a small hole (105 of FIG. 5) of the nozzle with the paint.